In the Cognitive Radio System (CRS), the spectrum sensing technologies are mainly used to sense a spectrum usage status in the network so as to subsequently determine a mode in which the spectrum is used. Specifically, a user equipment (UE) which is to communicate in the CRS must firstly confirm whether any other UE is communicating in the transmission frequency band so as to avoid interferences to the UE that is communicating in the transmission frequency band. In the prior art, this is confirmed mainly through an autocorrelation signal detector or a cross-correlation signal detector.
In detail, after receiving a radio signal in the transmission frequency band, the autocorrelation signal detector performs amplification, analog-to-digital (A/D) conversion, autocorrelation signal operation and sampling averaging on the radio signal directly through a single signal processing path, and compares the sampling average obtained with a signal threshold value. If the sampling average is greater than the signal threshold value, then it is determined that the radio signal comprises a signal of another UE; and otherwise, it is determined that the radio signal does not comprise a signal of any other UE.
On the other hand, after receiving a radio signal in the transmission frequency band, the cross-correlation signal detector performs amplification, A/D conversion, cross-correlation signal operation and sampling average on the radio signal through two signal processing paths, and similarly, compares the sampling average obtained with a signal threshold value. If the sampling average is greater than the signal threshold value, then it is determined that the radio signal comprises a signal of another UE; and otherwise, it is determined that the radio signal does not comprise a signal of any other UE.
However, the aforesaid autocorrelation detector technology uses only a single signal processing path, so noises produced during the signal processing has a direct influence on the subsequent determination result and greatly degrades the accuracy of the detector. On the other hand, although the cross-correlation detector that uses two processing paths can avoid the direct influence from the noises and slightly improve the accuracy of the detector, only a single signal cross-correlation value can be generated by the two signal processing paths and, therefore, improvement of the accuracy and the efficiency is relatively limited.
Accordingly, efforts have to be made in the art to provide a solution that can accurately determine the usage conditions of frequency bands and avoid interferences to communications of other users by significantly improving both the accuracy of the spectrum sensing detector and the usage efficiency of hardware.